The OTFS overlay for OFDM represents one approach to obtain the time domain signal from its DD representation. Like the Fourier transform, which represents the fundamental transform associated with OFDM, the so-called Zak transform can be associated with OTFS, as pointed out in [1]} and [2]}. In this context, the DD domain and the Zak domain are equivalent. Instead of mapping the symbols residing in the DD first to the TF domain and then to the time domain, the Zak transform directly maps the symbols onto a time-domain signal. A formulation of OTFS based on the continuous Zak transform was recently presented in [3]}.
